zggev eigenvalue question

[rickrho]

I have written a code that uses zggev successfully to compute the eigenvalues and right eigenvectors of a general complex eigenvalue problem. However my matrix is very large and I only need one of the eigenvectors for my calculations. Once zggev returns the eigenvalues and vectors I select the eigenvalue that is within the appropriate range, then output it's corresponding eigenvector. I have been trying to find a way to compute the single eigenvector separately, with zggev providing only the eigenvalue, this would speed up my code considerably. Setting up the system of equations with the appropriate eigenvalue is straighforward, but I cannot find a routine that will only compute the eigenvector or a specified eigenvalue, does one exist, if so where might I find it?

Also I'm solving this eigenvalue problem at successive points as one marches downstream in a fluid flow, my eigenvector shapes look correct for a single station, but they do not grow consistently as one marches downstream, I know that zggev normalizes it's eigenvectors, is it safe to assume that this normalization is consistent between different computations, or could the normalization be causing the erratic growth? Is there a way to ensure that normalization is consistent between different calls to zggev? My eigenvalues grow smoothly as one marches downstream, which leads me to believe my input is correct.

Thanks,
-Rick